1. Field of the Invention
The present invention relates to a blind which includes a head box, ladder-shaped supporting cords vertically extending from a bottom of said head box, a plurality of horizontal slats supported by said ladder-shaped supporting cords in vertically spaced relation to each other, a bottom rail disposed at the bottom of said plurality of horizontal slats, and lifting cords for raising or lowering said plurality of horizontal slats, each lifting cord vertically extending from the bottom of the head box through cord passing holes formed in the respective slats and being connected, at its lower end, to said bottom rail, wherein the slats are arranged to be raised or lowered by means of the lifting cords and to be tilted by means of said ladder-shaped supporting cords in order to adjust light-shielding effect of the blind.
2. Description of the Prior Art
Recently, in the field of the blind of this kind, there has been developed a blind in which each of the slats has an angle-shape in section and the cord passing hole is formed at an apex portion of said angle-shape. FIGS. 1 and 2 illustrates an example of the blind of this kind. In FIGS. 1 and 2, 1 designates a slat having an angle-shape in section, and 2 designates a cord passing hole for passing a lifting cord therethrough which is formed at an apex portion of said angle-shape. As shown in FIG. 3, a plurality of such slats 1 are supported by means of ladder-shaped supporting cords 4 which vertically extend from a bottom of a head box 3 downwardly. Each of lifting cords 5 for raising or lowering the slats comes out from a center position of the bottom of the head box 3 and extends through the cord passing holes 2 formed in the respective slats 1. The lifting cord 5 is connected, at its lower end, to a bottom rail 6 disposed at the bottom of the plurality of slats 1. These slats 1 are arranged to be raised or lowered by pulling the lifting cords 5 into or out of the head box 3 and to be tilted by relatively moving front and rear cord portions of the ladder-shaped supporting cords in vertical direction, thereby adjusting light-shielding effect of the blind.
In the blind including the slats having the angle-shape in section, when the slats are tilted by the ladder-shaped supporting cords, as explained above, the inner edges of the cord passing holes formed in the respective slats come into contact with the lifting cords, thereby hindering the tilting action of the slats so that it is difficult to tilt the slats to the desired vertical positions.
In the conventional blind of this type, slats having arcuate-shape in section have been usually used. The inventors have recently developed a new type of blind which includes arcuate-shaped slats, each of which is formed with many small pores, thereby forming a semi-light-transmitting slat (which is called as a "punched slat"). The blind using the punched slats of this type has such characteristic feature that when the blind is completely closed by tilting the slats to their vertical positions, the outside can be seen from the inside of a room while shielding a sun light, that is very convenient in practical use and this blind presents a superior external appearance. This blind has a good reputation for such characteristic feature, but has such defect that when the outside becomes dark, while the inside of the room is light, it is difficult to completely keep the inside of the room out of sight from the outside. This blind has a further defect in that a cord passing a hole for passing a lifting cord is relatively large and it is difficult to completely avoid the leakage of light through the cord passing hole.